Biotechnology: and its Application VBQ Class 12 Biology

VBQs For Class 12

Please refer to Biotechnology: and its Application VBQ Class 12 Biology with solutions provided below. These VBQs for Class 12 Biology with solutions have been designed as per the latest syllabus and NCERT books fror Class 12 Biology issued by CBSE, NCERT, and KVS. Students should revise all important topics and then also learn the value based questions provided below.

VBQ Class 12 Biology Biotechnology: and its Application


Question. State the role of C-peptide in human insulin.
Answer. The C-peptide is an extra stretch of the peptides that connects the A and B-polypeptide chains of insulin, in prohormone. During processing to release mature and functional insulin, this C-peptide is removed. 

Question. Name any two techniques that serve the purpose of early diagnosis of some bacterial/viral human diseases. 
Answer. Techniques that serves the purpose of early diagnosis of some bacterial/viral human diseases. (i) Polymerase Chain Reaction (PCR). (ii) DNA recombinant technology and (iii) ELISA are the techniques for early diagnosis of bacterial/viral diseases 

Question. How does ds RNA gain entry to eukaryotic cell to cause RNA interference?
Answer. dsRNA gain entry to eukaryotic cell either through: (i) infection by virus having RNA genome or (ii) mobile genetic elements (transposons) that replicate via an RNA intermediate.

Question. Name the source organism of the gene cry I Ac and its target pest. 
Answer. Source of gene cry l Ac is Bacillus thuringiensis and its target pest-cotton bollworms. 

Question. Name the cry genes that control cotton bollworm and com borer respectively.
Answer. The cry genes that control Cotton boll worm – cry l Ac and cry ll Ab Corn borer-cry l Ab 

Question. What is the significance of the process of RNA interference (RNAi) in eukaryotic organisms?
Answer. RNA interference (RNAi) acts as cellular defence in all eukaryotic organisms

Question. How does silencing of specific mRNA in RNA interference prevent parasitic infection?
Answer. Parasitic infection can be prevented by using RNA interference (RNAi) process, as the nematode cannot live in the transgenic host that expresses the specific interfering RNA thus, making it double stranded and unable to translate the protein or product.

Question. How are tobacco plants benefited when nematode specific genes are introduced into them using certain vectors? Name the vectors used.
Answer. Nematode specific genes when introduced into the host plants, initiate the process of RNAi and hence, silenced the specific mRNA of nematode. The parasite cannot survive in transgenic host, so prevent the plants from pests. Vector used is Agrobacterium.


Question. State how was Agrobacterium tumefaciens been made as a useful cloning vector to transfer DNA to plant Cells
Answer. The bacterium Agrobacterium tumefaciens is known to be natural vector capable of passing its DNA to plants and induce tumour by integrating its DNA with host genome. The tumour causing gene in the plasmid of this bacteria is replaced by gene of interest and is now used as a cloning vector to transfer the DNA into plant cells.

Question. Explain how Eli Lilly, an American company, produced insulin by recombinant DNA technology.
Answer. Insulin production by Eli Lilly company
(i) DNA sequences corresponding to the two polypeptide, A and B-chains of insulin are synthesised in vitro.
(ii) They are introduced into plasmid DNA of E. coli.
(iii) This bacterium is cloned under suitable conditions.
(iv) The transgene is expressed in the form of polypeptides A and B, secreted into the medium.
(v) They are extracted and combined by creating disulphide bridge to form human insulin.

Question. What do ‘cry genes’ in Bacillus thuringiensis code for? State its importance for cotton crop.
Answer. ‘cry genes’ in Bacillus thuringiensis codes for toxic insecticidal proteins that exist as inactive prototoxins. These proteins when expressed in cotton crops through genetic engineering confers pest resistance against cotton bollworms and prevents damage. As the larva of these insects when feed upon cotton plant parts, the toxin gets activated in their gut, lysing their cells and leads to death thus, making them pest resistant.

Question. Human insulin when synthesised in the body needs to be processed before it can act. Explain
Answer. Human insulin when initially synthesised in human body consists of three peptide chains- A, B and C. The C-peptide is an extra stretch of amino acids joining the A and B-chains. This is called proinsulin or prohormone. It undergoes processing or splicing to release the functional mature insulin that can carry out its normal functions. During processing, the C-peptide is removed. Only A and B-chains contribute to form the functional insulin.

Question. Name the disease that was first to get the gene therapy treatment. Write the cause of the disease and the effect it has on the patient.
Answer. The ADA (Adenosine Deaminase) deficiency disease was the first to get the gene therapy treatment. The disease is caused due to the deletion of gene that codes for Adenine Deaminase (ADA) enzyme. The deficiency of the ADA enzyme effects the functioning of immune system.

Question. Why is proinsulin so called? How is insulin different from it?
Answer. Proinsulin contains an extra stretch called C-peptide that needs to be removed to become fully mature insulin, therefore it is called proinsulin (prohormone). The mature functional insulin contains only A and B-peptide chain

Question. Highlight any four advantages of Genetically Modified Organisms (GMOs).
Advantages of GMOs are as follows:

(i) Tolerance against abiotic stresses, such as cold, drought, salt, heat.
(ii) Reduces dependence on chemical pesticides.
(iii) Reduce post-harvest losses.
(iv) Increase efficiency of mineral usage by plants.

Question. Expand ELISA. On what principle is ELISA test based? List two ways by which an infection can be detected by this test.
Answer. ELISA – Enzyme Linked Immuno Sorbent Assay. ELISA is based on antigen-antibody interaction. The two ways to detect the presence of infection or disease by ELISA are as follow: (i) The presence of antigens (proteins, glycoproteins, etc) are detected.
(ii) Antibodies produced against the pathogen are detected.


Question. Name the host plant and its part that Meloidogyne incognita infects. Explain the role of Agrobacterium in the production of dsRNA in the host plant.
Answer. The nematode Meloidogyne incognita infects the roots of tobacco plants.
The Agrobacterium are used as vectors carrying nematode specific genes to be introduced in host plant. These genes when expressed inside host plant produces sense and anti-sense RNA strands, complementary to nematode’s functional mRNA. This binding results in formation of double stranded RNA and inhibiting or silencing the translation of RNA specified. This process is called RNA interference.

Question. (i) Tobacco plants are damaged severely when infested with Meloidogyne incognita. Name and explain the strategy that is adopted to stop this infestation,
(ii) Name the vector used for introducing the nematode specific gene in tobacco plant.
Answer. (i)Infestation of tobacco plant can be stopped by using RNA interference (RNAi) process. Process of RNAi Process of RNA interference (RNAi) is related with silencing of a specific mRNA. It is a method of cellular defence in all eukaryotes.
(i) A complementary RNA binds to the mRNA making it double stranded and prevent its translation.
(ii) This complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.
(iii) Using Agrobacterium vectors, nematode specific genes were introduced into the host plants.
(iv) It produces both sense and anti-sense RNA in the host cells.
(v) These two RNAs being complementary to each other form a double stranded RNA (dsRNA) that initiated RNAi, silencing the specific mRNA of the nematode.
(vii) Due to this, parasite could not survive in a transgenic host expressing interfering RNA. So, transgenic plant is protected.
(ii) Vector used for introducing the nematode specific gene in tobacco plant is Agrobacterium.

Question. Explain the effect of deletion of the gene for ADA in an individual.
(ii) How does the gene therapy help in this case?

Answer. (i) Deletion of the gene for ADA in an individual lead to ADA deficiency disorder. Adenosine Deaminase (ADA) enzyme is crucial for immune system to function.
(ii) Gene therapy is helpful in case of ADA deficiency. Hereditary disease can be corrected by gene therapy. It is a collection of methods that allows correction or replacement of defective gene. The first gene therapy was given in 1990 to a 4 years old girl with Adenosine Deaminase (ADA) deficiency. It is caused due to the deletion of gene for adenosine deaminase.

The treatment involves following steps:
(i) Lymphocytes from the blood of patient are grown on culture outside the body.
(ii) A functional ADA, cDNA (using a Retro viral vector) is then introduced into these lymphocytes.
(iii) Such genetically engineered lymphocytes are returned to the blood of patient.
(iv) Periodic infusion of such genetically engineered lymphocyte is required by the patient.

Question. How did Eli Lilly company go about preparing the human insulin? How is the insulin thus, produced different from that produced by the functional human insulin gene?
Answer. Insulin production by Eli Lilly company
(i) DNA sequences corresponding to the two polypeptide, A and B-chains of insulin are synthesised in vitro.
(ii) They are introduced into plasmid DNA of E. coli.
(iii) This bacterium is cloned under suitable conditions.
(iv) The transgene is expressed in the form of polypeptides A and B, secreted into the medium.
(v) They are extracted and combined by creating disulphide bridge to form human insulin.

Question. (i) Why are restriction endonucleases, so called?
(ii) What is a palindromic, nucleotide sequence? How do restriction endonucleases act on palindromic sites, to create sticky ends?
 (i) Restriction endonucleases are so called because they recognise and make a cut at specific positions within the DNA and restrict the growth of bacteriophage. (ii) (a) The palindrome in DNA is a sequence of base pairs that reads same on the two strands of DNA when orientation of reading is kept the same. For example, 5’—GAATTG—3′ 3’—CTTAAG—5′ (b) Restriction enzymes cut the strand of DNA a little away from the centre of palindrome site, but between the same two bases in both the strands. This creates single stranded stretches, overhanging at the ends of the palindrome, called sticky ends.

Question. How are the following used in biotechnology?
• Plasmid DNA
• Recognition sequence
• Gel electrophoresis
Answer. (i) Plasmid DNA It is used for constructing recombinant DNA, by ligating the alien piece of DNA with it. It is used as a cloning vector and helps in the selection of recombinants from non-recombinants.
(ii) Recognition sequences These are specific base sequences of DNA, where restriction enzyme cuts the DNA. They are utilised to extract the desired gene or fragments from DNA molecules.
(iii) Gel electrophoresis It is a technique, used to separate the DNA fragments according to their size through sieving effect of the gel.

Question. Why are genes encoding resistance of antibiotics considered useful selectable markers for coli cloning vector? Explain with the help of one example.
Answer. The genes encoding resistance to antibiotics are considered useful selectable markers because the normal £. coli cells do not carry resistance against any of these antibiotics. Example A foreign DNA is ligated at the Bam HI site of tetracycline resistance gene in the vector pBR322. The recombinant plasmids will lose tetracycline resistance due to the insertion of foreign DNA but can still be selected from non-recombinants by plating the transformants on ampicillin containing medium. The transformants growing on ampicillin containing medium are then transferred on medium containing tetracycline. The recombinants will not grow, while non-recombinants will grow on the medium containing both the antibiotics. Antibiotic resistance gene, thus helps in selecting the transformants.

Question. How is the amplification of a gene sample of interest carried out using Polymerase Chain Reaction (PCR)?
Answer. Amplification of gene is done using polymerase Chain Reaction (PCR). it is carried out in the following steps:
(i) Denaturation The double stranded DNA is denatured by applying high temperature of 95°C for 15 seconds. Each separated strand acts as a template.
(ii) Annealing Two sets of primers are added, which anneal to the 3′ end of each separated strand.
(iii) Extension DNA polymerase extends the primers by adding nucleotides complementary to the template provided in the reaction. Taq polymerase is used in the reaction, which can tolerate heat. All these steps are repeated many times to get several copies of the desired DNA.

Biotechnology: and its Application VBQ Class 12 Biology